There are methods for grinding the teeth of a bevel gear in the discontinuous method (intermittent indexing process), which is referred to as the single indexing method. The present invention relates to the discontinuous grinding of bevel gears, i.e., pinions and crown gears, whose tooth gaps are prefinished by a chip-removing method (e.g., milling).
Because the requirements in regard to the load capacity, precision, and quiet running have risen for the correspondingly manufactured gear wheels, these manufacturing methods have been refined and optimized.
In the single indexing method, one tooth gap after another is finish machined using a grinding disc. Grinding discs which may be dressed are preferably used for this purpose. When grinding pinions (also referred to as drive bevel gears) and crown gears machined in the single indexing method, a disproportionately high wear occurs at the beginning of the machining process on the freshly dressed grinding disc, which is also known as rapid wear. On one hand, this wear of the grinding disc has the result that the geometry of the grinding disc changes. This has the result that the tooth thickness also changes, if one does not compensate for this change of the geometry of the grinding disc by the setting of the machine data. This form of compensation, which is applied in the mass production of bevel gears for vehicles, for example, may be achieved by a specific restraint of the grinding disc. A corresponding linear compensation is shown in FIG. 2.
On the other hand, however, a change of the surface texture (micro-geometry) of the tooth flanks results due to the rapid wear. The first tooth flanks which were manufactured using the freshly dressed grinding discs have a different surface texture than those tooth flanks which were manufactured later using the same grinding disc. These micro-geometry differences are frequently accepted in regard to the short cycle times which are available in mass production, although the quiet running of such bevel gear sets is thus negatively influenced in particular.
In bevel gears which require an identical surface quality of all tooth flanks, until now the grinding machining was performed in multiple passes, which requires an additional time outlay.
It is therefore an object of the invention to provide a method and corresponding software which allow bevel gears to be produced having identical surface quality of all tooth flanks, with the simplest possible means and without drastic lengthening of the cycle times.
The object is achieved by a method having the features of the present invention. According to this method, after the dressing of a grinding disc, a number of artificial tooth gaps (also referred to as virtual tooth gap(s)) are manufactured on the workpiece, to thus bridge the rapid wear phase as quickly as possible. The surface texture is different in the artificial tooth gaps which were thus manufactured than in the tooth gaps which are now subsequently manufactured. However, because the artificial tooth gaps are reworked, or post-processed, during the subsequent manufacturing of the tooth gaps, these tooth gaps also receive a flank surface which is identical or nearly identical to the surface of all other tooth flanks.
In other words, the invention is based on one or more prior tooth systems having been worked out on the workpiece, before all tooth gaps are then processed using the grinding disc, after this disc has “overcome” the rapid wear phase.
These artificial tooth gap(s) or prior tooth system(s) is/are machined according to the invention while the freshly dressed grinding disc is held in a restraint position. I.e., the grinding disc does not plunge as deeply into the tooth gap to be manufactured in this restraint position as it does after the rapid wear phase has been overcome.
Advantageous embodiments of the method according to the invention and/or the corresponding software are further described.